This invention relates to electrical fuses, and more particularly to a novel plug-in type fuse suitable for low voltage applications, and designed to be releasably pluggable into a female receptacle. In addition this invention relates to a method of making such fuses.
There are a number of plug-in type fuses that are currently employed for protecting low voltage circuits in automobiles and the like. These plug-in fuses have to a great extent replaced the older, glass tube fuses of the type in which a thin, wire fuse element is enclosed in glass tube, and is soldered or otherwise secured at opposite ends to metal caps that are secured over opposite ends of the tube.
Typically the plug-in type fuse (see, e.g., U.S. Pat. No. 3,909,767) includes a plastic housing containing a thin, metal fuse element, which is secured at opposite ends to a pair of flat, blade-shaped terminals that project out of the housing to be insertable into a matching female receptable. Ideally such fuses are designed so as to be easily insertable into a panel in side-by-side relation to protect a plurality of low voltage circuits, and to be readily accessible in the event they need be replaced.
A major disadvantage of these blade-type fuses is that they are relatively expensive to manufacture, and generally cannot be calibrated once they have been assembled. Efforts have been made to improve upon fuses of this type by using a single, one-piece metal fuse element having a pair of flat terminals interconnected by an integral, necked-down section, as disclosed for example, in the above-noted U.S. Pat. No. 3,909,767. An advantage of this construction is that the one-piece fuse elements can be stamped from a metal plate and then secured in respective plastic housings. The fuses are calibrated at the time that the elements are stamped from the metal plate, simply by predetermining the size of the necked-down portion which will be formed by the stamping operation. Among the disadvantages of this construction, however, is that the resultant fuse is rather expensive. Moreover, once the element has been stamped from a plate, its rating has been set, and further calibration thereof is not possible.